Bio-Processing Case Study: Sampling, Monitoring, & Control for Gas Fermentation to Fuel & Chemicals Derek Griffin CPAC Summer Institute 20 July, 2011 University of Washington © 2011 LanzaTech Inc. All rights reserved. The LanzaTech Process Novel gas fermentation technology captures CO-rich gases and converts the carbon to fuels and chemicals Gas feed stream Gas reception Compression Fermentation Recovery Product tank • Gases are sole source of energy • Production of fuels and chemicals • Potential to make material impact on the future energy pool (>100s of billions of gallons per year) • Completely outside of the food value chain • Biofuel and carbon capture technology solution 2 Making H2 On Demand LanzaTech can use a Hydrogen free-gas for the production of ethanol The ethanol molecule contains 6 Hydrogens: CO + H2O CO2 + H2 [H2] • Microbe can make H2 from CO and water as required Reduces Need for • Any CO:H2 ratio can be used Thermochemical WGS, Improving Overall C Balance 3 Feedstock Flexible Gas Composition Industrial Fuels & Chemicals Flue Gas e.g. from Steel Mill Gas-to-liquid Conversion CO Syngas Coal Municipal Solid Waste (MSW) Reformed Methane e.g. Biogas H2 Biomass A broad range of CO:H2 ratios can be used by the LanzaTech process Fuel production has been demonstrated with a wide range of available waste gas resources 4 LanzaTech Gas to Liquid Platform H H Resources CO CO 2 2 CO2 CO2 Industrial Syngas: Biomass, Coal, Methane COG, Chemical Power Native Customized Engineering Control Catalysts Synthetic Chemistry C2 C3 C4 C5 Other • Ethanol • i-propanol • BDO • Isoprene • PHB Product Suite • Acetic acid • n-Butanol • ……. • i-Butanol • Succinic acid Thermochemical Approaches Hydrocarbon Fuels Product Suite (diesel, jet, Chemical Chemicals gasoline) Intermediates Olefins 5 Process Overview 3 Main Sections to LanzaTech Process – Gas Conditioning – Anaerobic Gas Fermentation – Product Recovery 6 Gas Conditioning & Clean-up Key Measurements: – Inlet gas composition – On-line Gas Chromatography (GC) • Measure CO, CO2, N2, H2, CH4, O2, & H2S – Gas temperature and pressure – Gas flowrate Bioreactor system operates at 8-10 bar – Low pressure gases require up to 4 compression trains – Compression sizing and design based on inlet gas flowrate, pressure, and overall composition – Need to account for pressure drop through deoxygentation and gas-cleanup 7 Deoxygenation Anaerobic fermentation requires reduced oxygen content O2 levels < 100 ppm – Deoxygenation vessel size, temperature, and residence time based on gas flowrate, inlet O2 level, and catalyst activity Continuous gas streams require accurate O2 measurement in and out of deoxygenation bed – Simple feed-forward and feed-back control can be used for changes in inlet and outlet gas respectively Some gas streams are intermittent (steel mill BOF gas) requiring gas holder(s) – Improved process robustness with multiple gas holders that can be tested for O2 & contaminant levels before using gas as fermentation feed 8 Gas Clean-up LanzaTech process can tolerate high levels of impurities so extensive gas cleanup may not be necessary – Microbes tolerant to H2S up to 2% • Can be measured by GC – Currently testing BTEX up to 500 ppm in laboratory – Contaminant testing currently performed off-line to measure levels of BTEX, HCN, NH3, etc.. Microbes require low level of sulfur in fermentation broth – Inlet gas may provide sulfur in form of H2S eliminating requirement for sulur component in media preparation 9 Contaminants The addition of multiple potentially toxic, Gases, Metal Ions and organic contaminants have been tested off-line: H S: 2% in gas feed Chromium: (II) 2mMol/L 2 500ppm (III) 100mMol/L SO 2: NO X: 50ppm Benzene: 0.12 mol% in gas Vanadium: 10µMol/L Toluene: 0.008 mol % in gas Bromide: 100µMol/L 100µMol/L Iodide: 50µMol/L Copper: CO : >50% in gas Arsenic: 12μmol/L 2 Methane : >50% in gas N2: >50% in gas HCl : Buffered in media Goal: Certain gases will contain different impurities; need various on-line low level impurity measurement for different gas feeds 10 Fermentation System – Bioreactor Air-lift bioreactors are commonly used for fermentation over stirred tank reactors – Gas well mixed – Homogeneous 3-phase mixture – No agitator or stirrer, minimal cell shear & lower power consumption – Pressure difference between riser and downcomer aids in fluid circulation – Fewer internal moving parts = better sterilization Internal Loop Reactors External Loop Reactors 11 Mass Transfer Estimation CL – conc. of gas in liquid C* - gas solubility in liquid kL – overall mass transfer coefficient aL – specific interfacial area dCL Measure of reactor inlet, Cin, & outlet CO composition determines dt Gas solubility, C*, depends on headspace pressure & reactor temperature which are monitored and controlled Other variables that contribute to G/L mass transfer – Gas/liquid holdup – Bubble size/number distribution effects aL – Gas velocity (mean residence time) effects boundary layer and kL 12 – Mixing times & Turbulent/Laminar Flow also effects kL Potential Control Structures Multiple inputs/outputs & complicated process model combining 3-phase bioreactor hydrodynamics and microbial reaction system – Numerous unique bioreactor ‘scenarios’ and overall system non-linearity eliminate use of simple feedback control Model predictive control requires extensive data-base covering all possible ‘scenarios’ Fuzzy Logic – apply a ‘truth value’ to variables in different scenarios Neural Net - more complex, adaptive, computational model. Can be taught or trained on various scenarios Goal : singular structure that can be programmed to handle batch start-up, Artificial neural network transition to continuous mode, and dynamic transition to steady-state 13 Product Recovery & Waste Water Treatment Product recovery & waste water systems mature technologies with well developed control structures 1. Broth concentration measured entering recovery section 2. Metabolites leaving product recovery measured entering water treatment 3. Nutrients and metabolites measured in water recycle to media preparation – Need to be able to accurately measure low levels of salts & minerals Anhydrous ethanol product, waste water purge, & biomass purge also monitored to ensure within target specifications 14 Media Preparation Continuous media preparation requires inputs from gas stream composition and nutrient concentration in water recycle Water treatment & gas flow is continuous while media is prepared in batches Currently Investigating dissolved O2 measurement in media – Requires costly in-situ monitor that can measure ppb levels 15 Summary LanzaTech’s gas fermentation technology differs from conventional biological fermentation processes due to gasesous feedstock and G/L mass transfer issue of nearly insoluble gases Conventional sampling, monitoring, and control can be achieved for gas conditioning and product recovery sections Biggest challenge surrounds bioreactor – In-situ measurements of G/L ratio, dissolved CO, metabolite & nutrient concentrations are current challenges – Numerous inputs & outputs based on biological system requires detailed process model & complicated control structure – Bioreactor & microbial behavior can drastically change depending on microbe, gas feed, and/or metabolites produced requiring unique process models and control schemes 16 Questions & Comments: [email protected] 17 .